1. Technical Field
Example embodiments of the present invention relate to a wireless communication technology, and more specifically, a method for individual nodes which are components of a wireless network requiring network synchronization to acquire network synchronization.
2. Related Art
A type of synchronization used in a wireless network may be classified into a packet synchronization (or, a link-level synchronization) and a network synchronization.
In a case of the packet synchronization, a receiver should know a start position of a packet and a modulation symbol timing of the packet in order to perform demodulation on the packet. A transmitter may transmit a training sequence or a preamble (PR) as included in a former part of the packet in order to notify the receiver the start position of the packet and make the receiver be able to perform demodulation by symbol timing recovery. In this case, the transmitter may transmit the packet at any time when it is necessary, and definitions on a packet transmission start time or packet transmission length are not necessary.
On the contrary, the network synchronization is a type of synchronization in which a start position and a length of a frame or a slot should be predefined. The start position and length of a frame and a slot, which can be recognized by all nodes in a wireless network, are configured identically. The transmitter should use a specific frame or a specific slot to transmit a packet.
On the other hand, a wireless network may be controlled in a centralized manner or in a decentralized manner. In a case of the centralized manner, a concentration node (for example, a base station) may be responsible for transmission, resource allocation, and control of synchronization signals required for network synchronization. However, in a case of the decentralized manner, since the concentration node does not exist, the above functions may be performed autonomously or automatically by individual nodes.
A Carrier Sense Multiple Access/Collision Avoidance (CSMA/CD) of IEEE 802.11 is a well-known algorithm supporting the above mentioned decentralized control manner. It is based on an Orthogonal Frequency Division Multiplexing (OFDM), and requires a link-level synchronization. However, it does not require a network synchronization. Therefore, the decentralized control manner used in the IEEE 802.11 may be strictly represented as ‘an asynchronous CSMA/CA based on OFDM’.
It is well-known that enhancement of system throughput and effect of decreasing power consumption may be achieved in an environment to which network synchronization is applied. Also, it is well-known that an Orthogonal Frequency Division Multiple Access (OFDMA) makes flexible and efficient use of frequency resources possible as compared to the OFDM. Although the system based on the OFDM may select at least one of link-level synchronization and network synchronization, the system based on the OFDMA should adopt network synchronization.
As described above, the network synchronization provides advantages which cannot be given up on many aspects for both the OFDM system and the OFDMA system.
However, a detail method for each node in an environment based on decentralized control manner to acquire network synchronization has not been proposed until now.